Electronic calculator systems of the type wherein all of the main electronic functions are integrated in a single large cell integrated semiconductor chip or in a small number of such chips, are described in the following U.S. Patents, which are assigned the assignee of this invention:
U.s. pat. No. 3,919,532 issued to Michael J. Cochran and Charles P. Grant on Nov. 11, 1975 are entitled "CALCULATOR SYSTEM HAVING AN EXCHANGE DATA MEMORY REGISTER". PA1 U.s. Pat. No. 3,934,233 issued to Roger J. Fisher and Gerald D. Rogers on Jan. 20, 1976 and entitled "READ-ONLY-MEMORY FOR ELECTRONIC CALCULATOR". PA1 U.s. pat. No. 3,931,507 issued Jan. 6, 1976 to George L. Brantingham entitled "POWER-UP CLEAR IN AN ELECTRONIC DIGITAL CALCULATOR".
The concepts of these prior applications have made possible vast reductions in the cost of small personal-size calculators. Continuing efforts to reduce the cost of these products include the design of a single chip calculator system for use in large capacity calculators, such as scientific or business calculators. The chip disclosed herein may be utilized in scientific or business calculators for instance, because this chip has provisions for a number of storage registers, in addition to operational registers, as well as sufficient capacity to solve the more complicated mathematical expressions and functions used in scientific and business calculators including, for example, trigonometric and logarithmic relationships.
The present invention relates to a combined data and flag bit storage system for microprocessor and more specifically a combined data and flag bit storage system for a word organized electronic calculator. An entire electronic calculator system including the combined data and flag bit storage system of this invention is disclosed. The electronic calculator disclosed is a serial, word organized calculator. Data is transferred within the calculator system in serial format as opposed to transferring data in parallel format as done by calculators disclosed in the aforementioned U.S. Pat. Nos. 3,919,532 and 3,934,233. It should be evident, however, that this invention is not limited to serial calculator systems.
Prior art calculators, for instance, of the type disclosed in U.S. Pat. No. 3,919,532, were normally provided with separate memories for storing data and for storing flag bit information. This separation generally required that the calculator system be provided with an arithmetic unit for accomplishing arithmetic operations on the data stored in one memory in addition to a flag logic unit for performing logical operations on the flag bits stored in another memory. In addition, the flags were not inherently associated with the data for which the flag bits may be used to represent the status of logical operations pertaining thereto.
It is therefore one object of this invention to provide a combined data and flag bit storage system for an electronic calculator. It is another object of this invention to provide a data storage system for storing both data words and associated flag bits in the same registers. It is yet another object of this invention to provide an arithmetic unit for performing arithmetic operations on the data words stored and for performing logical operations on flag bits stored in the data storage system.
The foregoing objects are achieved according to the present invention as is now described. In a preferred embodiment of the invention, a combined data and flag bit storage system is provided on a semiconductor chip, the combined data and flag bit storage system having a plurality of operational registers or memories each having a plurality of first and second bit storage locations, the first bit storage locations being provided for storing multi-bit data words and the second bit storage locations being provided for storing a plurality of flag bits associated with the data word. The operational registers are further interconnected with an arithmetic unit which is adapted to perform arithmetic operations on the data words and logical operations on the flag bits stored in the operational registers.